In a Taumel-type reclining device, on any one side of the seat cushion side and the seat back side, an internal gear is provided, and on the other side of the seat cushion side and the seat back side, an external gear having a smaller number of teeth than the number of teeth of the internal gear is provided so as to be engaged with the internal gear. The Taumel-type reclining device eccentrically moves one of the internal gear and the external gear around the rotation axis of the other gear while changing the engagement position of the internal gear and the external gear, thereby changing the tilting angle of the seat back with respect to the seat cushion.
FIG. 10 is a view for explaining the Taumel-type reclining device according to the related art. As shown in FIG. 10, in an eccentric annular space between the inner surface of a circular hole 1 and the outer surface of a cylinder 3, a pair of wedge-shaped members 5 and 7 is disposed. The pair of wedge-shaped members 5 and 7 is biased in directions (an arrow A direction and an arrow B direction) to drive wedges into the eccentric annular space by a spring 9.
The wedge-shaped members 5 and 7 each press the inner surface of the circular hole 1 and the outer surface of the cylinder 3, thereby pressing the internal gear and the external gear in a direction to increase eccentricity between the rotation axes of them. As a result, the inner teeth of the internal gear and the outer teeth of the external gear are deeply engaged with each other, whereby the seat back becomes a locked state in which the seat back does not tilt.
An abutting surface 11a of an unlocking cam 11 can press an end surface 5a or an end surface 7a of the tip side of the wedge-shaped member 5 or 7 against the biasing force of the spring 9, thereby pressing the wedge-shaped member 5 or the wedge-shaped member 7 in a wedge-shaped member drawing direction (the direction opposite to the driving direction: the direction opposite to the arrow A or B direction). If the wedge-shaped member 5 or the wedge-shaped member 7 are pressed to move by the unlocking cam 11, the pressing force which the wedge-shaped member 5 or the wedge-shaped member 7 applies to the inner surface of the circular hole 1 of and the outer surface of the cylinder 3 decreases, and the engagement of the inner teeth and the outer teeth becomes shallow, whereby the seat back becomes capable of tilting.
When one wedge-shaped member 5 or wedge-shaped member 7 starts moving, the other wedge-shaped member 7 or wedge-shaped member 5 is still due to friction with the inner surface of the circular hole 1 and the outer surface of the cylinder 3. However, if one wedge-shaped member moves in the wedge-shaped member drawing direction, the other wedge-shaped member quickly moves in a direction to drive the wedge into the eccentric annular space by the elastic repulsion force of the spring 9. While this operation is being repeated, eccentricity between the internal gear and the external gear is maintained, and the engagement portion varies, whereby the seat back tilts. That is, the seat back becomes an unlocked state (see Patent Literature 1 for instance).